1. Field of the Invention
This invention relates to gas pressure regulators and, more particularly, to gas pressure regulators for oxy fuel torches that are used to cut ferris metals. These cutting torches operate with a fuel gas and oxygen. Acetylene is a commonly used fuel gas; however, other types of fuel gas are also used, including, for example, natural gas, propane, hydrogen, and MAPP gas.
2. Description of Prior Art
Flashback is a term used to denote a situation which can occur in oxy fuel cutting torches and multi-purpose torches such as those described above. When a flashback occurs, it may cause damage to the equipment. In some instances, personal injury also results to the operator and/or those in proximity to the equipment. The present invention does not eliminate the occurrence of flashbacks. The purpose of the present invention is to reduce the possibility that a flashback, should it migrate from the torch upstream through the hose to the pressure regulator, will enter the oxygen and fuel cylinders.
Those skilled in this art are familiar with the components in a typical oxy fuel cutting system. The torch is releasably connected to an oxygen hose and a fuel gas hose. It is common in the industry for the oxygen hose to be colored green and the fuel gas hose to be colored red. These two hoses are typically assembled together to form a unitary hose bundle which is convenient for the operator to manipulate in the work place.
The oxygen hose is connected to a gas pressure regulator which is in fluid communication with a cylinder shut-off valve mounted on the oxygen cylinder or tank. Industrial oxygen cylinders are typically rated for pressures of up to 3000 lbs. per square inch (psi) although higher rated cylinders are available. The pressure regulator is used to variably reduce the outlet pressure coming from the cylinder and going into the hose. The outlet pressure from the pressure regulator needs to be variable, depending on the size of the cutting tip used. Generally speaking, the oxygen pressure at the outlet of the pressure regulator may range between 10 and 90 lbs. psi gauge ("PSIG"). Higher outlet pressures are used with high speed and larger sized cutting tips, while lower outlet pressures are used with lower sized cutting and welding tips. The appropriate outlet pressure from the pressure regulator is best determined by reference to a cutting tip chart which lists optimum pressures and flow rates for each different size tip. The oxygen connectors on the hose and regulator are a special size thread which is specified by the Compressed Gas Association ("CGA").
The fuel gas hose connects to a gas pressure regulator, identical to the gas pressure regulator for the oxygen cylinder, which is in fluid communication with the cylinder shut-off valve on the fuel gas cylinder or tank. Acetylene is a commonly used fuel gas for cutting torches, as described above. A typical acetylene cylinder is formed with an interior porus mass which is saturated with liquid acetone. Acetylene gas is absorbed by the liquid acetone to facilitate safe storage. When the cylinder shut-off valve is opened, the acetylene gas vaporizes and migrates to the top of the acetylene cylinder where it passes through the cylinder shut-off valve and the pressure regulator into the fuel gas hose which feeds the torch. Industrial acetylene cylinders are typically rated for pressures of 400 PSIG at 105.degree. F. Outlet pressures of acetylene at the pressure regulator vary, depending on the size of the cutting tip in use, but typically ranges between 1 and 15 PSIG. Larger cutting and heating tips and require higher pressures while smaller cutting and heating tips require lower pressures. Again, the operator should make reference to a cutting tip chart to determine optimal outlet pressures and flow rates. The fuel gas connectors on the hose and pressure regulator are special size left hand threads which are specified by the CGA to avoid confusion.
Flashback occurs when the flame front migrates from outside the torch tip to the inside of the torch, which causes the torch to become very hot and, if allowed to burn, may even cause it to melt. The flame front can also migrate upstream back into one or both hoses, causing them to burn or rupture. Furthermore, in some situations, the flame front may migrate further upstream into the pressure regulator and/or the gas cylinder, causing them to explode.
Various types of safety devices have been developed for use in typical oxy fuel cutting systems. For example, U.S. Pat. No. 4,286,620 assigned to Victor Equipment Company, the assignee of the present invention, which is specifically incorporated herein by reference, discloses a combination torch and check valve assembly. In the '620 patent, which issued on Sep. 1, 1981, the check valves are internal to the torch and are designed to reduce the possibility of reverse flow of gases from the torch into the hose.
U.S. Pat. No. 4,409,002 discloses a utility torch having a head mixer, which patent is specifically incorporated herein by reference. This patent is also assigned to Victor Equipment Company, the assignee of the present invention. The integral head mixer disclosed in the '002 patent, which issued on Oct. 1, 1983, is also designed to reduce the possibility of a flashback migrating from the torch upstream to other components in a typical oxy fuel cutting system.
Furthermore, U.S. patent application entitled "Torch with Integral Flashback Arrestors and Check Valves" filed Feb. 10, 1993 and preliminarily assigned Ser. No. 08/017734, and assigned to Victor Equipment Company, the assignee of the present invention, and which is specifically incorporated herein by reference, discloses a torch with an integral flashback arrestor assembly.
Other devices known generally in the art as "flashback arrestors" have been developed to reduce the possibility of migration of a flashback from the torch into the hose. These flashback arrestors are generally sold in pairs as after-market accessories. Victor Equipment Company also sells, as an accessory item, a pair of flashback arrestors which can be connected between the torch and the hose in the oxygen flow path and the fuel gas flow path. There is also a model that fits between the regulator and the hose.
The flashback arrestor manufactured by Victor Equipment Company is marketed under the trade name FLAMEBUSTER. It includes a porus, powdered metal sintered arrestor and check valve which is designed to reduce the possibility of a flashback from migrating upstream of the sintered component. The porus flashback arrestor has numerous tortuous pathways through which a flame front must pass in order to migrate further upstream into other components in an oxy fuel cutting system. In most circumstances, a flame front will be quenched as it attempts to move through the tortuous pathways in the porus flashback arrestor.
Victor Equipment Company also manufactures another accessory item which is marketed under the trademark FLAMEBUSTER PLUS. This accessory item includes a pair of flashback arrestors and check valves with quick hose connectors manufactured in a cartridge-like format. One cartridge is for oxygen and the other cartridge is for fuel gas. Numerous other competitors manufacture accessory units which include a flashback arrestor and check valves. These accessory items can be readily purchased from welding supply stores across the country.
Porous metal flashback arrestors, including the present invention, are not fool-proof devices and do not guarantee that the flame front will be quenched in all circumstances. For example, if the porous metal flashback arrestor is overheated, it may not quench the flame front. If the flashback arrestor has been exposed to numerous prior flashbacks, the tortuous pathways may be eroded, thereby reducing the quenching capability. The after-market flashback arrestors sold by Victor Equipment Company and others are not universally used in the trade. A pair of aftermarket flashback arrestors typically cost $40.00 to $60.00 (1992 Dollars). The additional cost deters some individuals from buying this after-market flashback arrestors and adding them to their oxy fuel cutting systems. Some individuals are simply not safety conscious and do not see a need for these accessory items. If a pair of accessory flashback arrestors have been installed on the job, they may sometimes be clogged with debris and be taken out of the system by the operator. Existing flashback arrestors sold as after-market items do not use the parts in place principle nor can they be repaired. If they are clogged or otherwise malfunction they must be replaced.
Some of these after-market accessory items are rather heavy and cumbersome and, if attached to the torch, may adversely affect the balance thereof which is irritating to the operator. Because these after-market accessories are readily removable, the operator may take them off of the torch.
Those skilled in the art will recognize that regulators are reconditioned on an as-needed basis. In a typical fabrication plant an operator will go to a tool crib and be issued a regulator for a specific project. At the conclusion of that project, the regulator will be returned to the tool crib. This sort of heavy industrial use eventually renders the regulator unsuitable for further cutting. The inlet filter may be clogged or other malfunction may occur such as damage to various components of the regulator. The tool crib foreman will have a large number of regulators in supply, depending on the size of the plant. When a regulator ceases to function properly, it will be set aside until a suitable quantity of malfunctioning regulators have been accumulated. These malfunctioning regulators will then be sent to a welding supply shop or to a reconditioning shop which will recondition the regulators and bring them back to operational specifications. Regulators manufactured by Victor Equipment Company are reconditioned during their usual life span which may be as long as 10 or 20 years. It may be necessary during the useful life of these regulators to replace the flashback arrestor, if any, on one or more occasions, depending upon the nature of use to which the regulators is exposed. Existing flashback arrestors are not subject to repair. They are to be replaced, and thus a new one must be purchased. This added expense deters replacement of flashback arrestors in existing systems during reconditioning.
The present invention includes a pressure regulator which has a replaceable flashback assembly which is formed as an integral part of the pressure regulator body. The flashback assembly is easy to replace and costs less than after-market flashback arrestors. This invention uses the parts in place principle (PIP) as an additional safety feature. If the flashback assembly is removed from the pressure regulator, the pressure regulator can no longer be connected to the torch hose.
The present invention does not prevent the occurrence of a flashback. Rather, the invention is designed to reduce the possibility that a flashback which does migrate upstream from the torch handle into the hose, regardless of whether a flashback arrestor is installed in the torch handle, will reach the gas cylinder. The invention is intended to provide an added measure of safety. The present invention is not fool-proof however, and, under certain circumstances, it will not prevent migration of a flashback into the cylinder.